Mercury boiler



, 1958 2 Sheets-SheffI l A. R. SMITH MERCURY BOILER,

Filed Aug'. 17

, 47 Inventor Arthur R. Svwwitr-w,

Hfs Attovney.

May 13, 1941.

2 Sheets-Sheet 2 May 13, 1941. A. R. SMITH MERCURY BOILER Filed Aug. 17, 1938 'Lz/f 63 Inventor Arthur 1Q. im it. r1

Att, o r" T1 e y Patented May 13, 1941 l l2,241,966l

' MERCURY Bonnin Arthur It. Smith, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York i Application August 17, 193s, serial Nc. 225,435

4 claims. (o1. 122-235) The present invention relates to mercury boilers comprising combustion and convection spaces with heating elements in which mercury is heated and partly evaporated. The circulation of mercury from a drum or like vessel through these heating elements may be effected either by natural flow or by pumping means. In the natural ow or circulation type boiler, mercury liquid is ordinarily conducted by downcomers external the furnace to the lower ends of heating tubes in which the mercury rises by thermo-syphon action caused by the formation of vapor in th'e up-tubes and by the difference in gravityv between the relatively cold mercury contained in the down-tubes and the relatively hot mercury contained in the up-tubes. In forced circulation type boilers the mercury is circulated or forced through heating elements by means lof a pump or pumps.v 'I'he thermo-syphon type mercury boiler using ordinary mercury, Without chemical treatment, has always been vulnerable and often not able to accept the heat of a modern furnace while the forced circulation boiler in which the mercury is forced downwardly and thereby capable of accepting more and more heat on its paththrough the uid circuit, requires considerable pumping energy which reduces the over-all emciency of such boiler.

The object of' my invention is to provide an improved construction and arrangement of mer- 'i cury boilers in which the principles of both the thermo-syphon and the forced circulation type boilers are combined to best advantage.

For a consideration of what I believe to be novel and my invention,attention is directed to the following description and the claims append? ed thereto in connection'fwith the accompanying drawings.

In the drawings, Fig. l illustrates a mercury boiler embodying my invention, and Fig. 2 shows a modication of my invention.

The arrangement of Fig. 1 comprises walls Ill forming a combustion chamber I I, walls I2 forming a convection chamber I3 and walls hi forming a bottom portion and connecting the lower end of the combustion chamber I I with the lower end of the convection chamber i3. Thewalls are :made of insulating and heat-resistant materials I5 covered outside by sheet metal I6. The bottom walls Iii and the walls I0 and I2 form sliding joints Il, It to permit relative movement between them during operation. The boiler walls are supported on a structure including vertical posts i@ and a plurality of horizontal beams 2b. Fuel and air for combustion are supplied to the combustion chamber through burners 2l connectedV to the ceiling of the ccmbustion chamber and directed downwardly whereby during operation combustion in the chamber I I progresses in downward direction and the combustion gases are conducted from the lower end of the chamber II to the lower end of the convectionchamber I3 in which they riseupward. The walls l0 in the combustion chamber are lined in the present instance with substantially vertically arrangedI radiation heating tubesy 22 and 23. The upper end portions of the tubes 22, 23 line the inclined ceiling in the combustion chamber and are connected to headers 24 and 25 re'spectively. Mercury Aliquid is forced into these headers 24, 25 by a mercury pump 26 which has an inlet conduit 21 connected to a vessel or drum 28 and discharge conduits 29 and 'connecte'd to the headers 24 and 25 respectively. The pump is drivenl by an electric motor 3l and flexiblyv supported, in the present instance hung up on beams 32 by means includingsprings 33. The lower ends ofv the tubes 22 and 2'3are connected to headers 34 and 35 respectively. The latter 'Y 4in turn are connected to the lower endsfof rows of convection tubes 36 and 31 lining thewalls in the convection chamber I3. The upper ends of at least-some of these convection tubes are connected to the upper ends of banks of heating tubes 38 located in an upper, enlarged portion of the convection chamber at a level above the level of the drum 28. These banks of heating tubes 38 include a plurality of separate tubes having hairpin-shaped portions through which the flow of fluid takes place in a general downward direction. With reference to the downward ilow these tubes may be designated inverted convection heating tubes or elements. The lower ends of the tubes 38 are connected `to the drum 28. The drum 28 and the end portions of the tube 38 are located in a lateral extension of the convection chamber whereby the drum does not obstruct the iiow of gases through the convection chamber and the end portions of the tubes 32 connected to the drum are protected from the direct heat in the convection chamber. The drum 23 includes a screen or baiiie 39 for directing the mixture of liquid mercury discharged from the inverted convection heating tubes in downward direction towards a pool, thereby to'prevent liquid particles from being carried away through a discharge conduit i0 connected to the drum liti. During starting the inverted convection tubes 38 being 'located above the level of the drum 2% are empty of mercury liquid. This reduces the amount of mercury liquid necessary for operating the boiler and at the same time these tubes constitute considerable additional heating sur-` face for mercury during normal operation.

During operation mercury liquid is forced by the action o1' the pump 26l into the upper ends of the down-tubes 22, 23 in the combustion chamber, whence it flows from the lower ends thereof through the up-tubes '31, 36 and finally through the inverted tubes 38 in the convection chamber into the drum 26. It will be noted that with this arrangement bothv up-tubes and downtubes, that is, all tubes carrying mercury and forming a part of the uid circuit, are located within the heating chamber. 'I'he down-tubes `22, 23 which receive mercury liquid directly from the drum are located in the combustion chamber and the up-tubes 36, 31 which receive heated mercury from the down-tubes as well as mercury liquidin the convection tubes 36, 31 and the inverted convection tubes 38. The dierence in gravity of the mercury contained in the tubes 22 and 36 causes upward ow of the mercury in the tubes 36 and, in addition, as just stated, the formation of vapor in the tubes 36 has a thermosyphon effect, that is, it increases the velocity of ilow through the convection tubes in the chamber I3' and consequently also the velocity of iiow through the radiation tubes in the chamber Il. In order to obtain maximum circulation in an ari rangement of this kind, it is important to prevent evaporation in the down-tubes 22, 23 because such evaporation would have an adverse effect on the circulation and might evencause reversed circulation. To this end it is important to provide means which permit evaporation only in the last part of the fluid circuit through which the mercury ilows in upward direction. 'Ihis last part of the uid circuit in the present instance constitutes the tubes 36 and 31. Thus, evaporation of the mercury is to be permitted only after it has passed through the headers 34, 35 near the lower ends oi.' the tubes 36, 31 respectively. vAn arrangement for controlling'the evaporation by varying the' speed of the circulating pump 26 is shown and will be described hereinafter in con nection with Fig-2.

The varrangement also includes means to permitV relative expansion between the tubes and q the adjacent walls of the boiler as well as to keep the tubes taut, thus preventing intermediate tube portions from moving away from the walls .of the combustion and the convectionchambers.

` To this end each tube has a plurality of spaced,

U-shaped members 4l welded to its back and located in recess 42 in theywall. The members i 4l are guided in openings of plates 43 which have portions embedded/in the wall and fastened to the outer vsheet metal cover I6. In this manner l the A'tubes may move vertically relative to theu wall. An arrangement of this kind is more fully described in an application of O. L, Wood, Serial No. 221,315, filed on July 26, 1338, and assigned to the same assignee as the present application. Portions of the tubes 23 lining the bottom portion are secured to the latterby means of link 44, in fact the bottom wall I4 is at least partly supported on the tubes 23 in the combustion chamber and the tubes 31 in the convection chamber, thus keeping the tubes 23 and-31v taut. Likewise, a wall portion 45 connecting the adjacent walls of the combustion and convection chambers lis supported on the tubes 22 and 36, thus keeping these tubes taut. In addition, the tubes 23, more specically lower bent portions 46 thereof, are pulled downward and laterally outward by a mechanism including springs 41 and 46. Likewise, the lower portions of the convection tubes 31 near the header 35 are pulled downward I`and laterally outward away from the the boiler by a mechanism including springs 56 and 5I. K 'Ihe arrangement of Fig. 2 comprises walls 65 forming a combustion chamber 56 and a convection chamber 51, the latter communicating at its lower end with the combustion chamber. Fuel is supplied to the combustion chamber by a burin-` er 58 supported on the ceiling of the chamber. The Awalls of the combustion chamber are lined with up-tubes 53 and down-tubes 60 and 6I connected to an upper header 62 and to lower headers 63, -64 and 65 respectively, the down-tubes 6l!v lining a rear wall of the combustion chamber being connected tothe lower header 64 and the down-tubes 6I lining a side wall being connected to the lower header 65. 'I'he convection chamber 51 contains up-tubes 66 connected at their lower ends to the headers 614 and 65 respectively and at their upper ends to a vessel or `drum 61 having a deiiector 63 and a discharge conduit 63.

Mercury liquid in this arrangement is forced from the drum 61 into the lower header 63 by means of a pump 10 having an inlet conduit 1| connected to the drum 61 and a. discharge conduit 12 connected to the header 63. From the header 63 the mercury is* forced through the uptubes 53 into theupper headerl 62, whence the mercury flows through the down-tubes 60 and 6| into the lower headers 64 and 65 respectively and finally from said headers through `the convection tubes 66 into the drum. The circulation of the, mercury, through the tubes inv the combustion` means are provided to prevent evaporation inthe tubes of the combustion chamber.

This mechanism comprises a temperature pressure differential responsive device including a temperature responsive device 13` ani a pressure responsive-device 14 having bellowsI connected to the ends of a `iloating lever 15, rwhich latter is pivotally connected to a lever supported on a fulcrum 16 and having an arm carrying a switch 11. The switch 11 forms part of a relay circuit including a contact-making member 13 for short-circuiting a resistance 19. 'Ihis resist' tance is connectedinto the circuit of a motor 30 for driving the pump 10. The pr Ssure and temmercury into the down-tubes, and means including a. device responsive to ,changes of the condition of the mercury near the lower ends of the tubes for controlling the circulation of mercury to prevent. evaporation of liquid in the y downtubes.

2. A mercury boiler comprising walls forming a combustion chamber and a convection chamber increased circulation of mercury liquid from the drum through the heating tubes and increase in pressure or drop in temperature of the mercury liquid contained in the header 65. temperature differential responsive device of this kind is more fully described in the Patent No.

2,088,623 to E. S. Thomson, issuedAugust 3, 1937, and assigned tothe same assignee as the present application. In the present arrangement this device serves to prevent evaporation of liquid before the liquid has reached a certain point in' the 4fluid circuit, more specifically before the liquid has entered the last up-tubes of the iiuid circuit.

While the combustion chamber in Fig. 1 includes down-tubes only, the combustion chamber in Fig. 2 includes both up-tubes and down-tubes,

the mercury being heated first in the uri-tubes and then in the down-tubes, which latter are connected in series with the up-tubes. The supply tubes 1|, l2 have been shown external the furnace to simplify the arrangement somewhat. Ordinarily in a boiler of the 'kind described it is desirable to place these tubes also inside the combustion space in the form of down-tubes lin- I ing the walls of the combustion chamber. Thus, an arrangement according to my invention includes one or several rows of series-connected vertically arranged up` and down-tubes lining the walls of a combustion chamber through which mercury is forced by means including a. motoroperated pump and from which heated mercury liquid is discharged at the lower end of the downtubes into the inlets of a plurality of up-tubes adjacent the combustion chamber and arranged to receive gases discharged from the latter, a drum located near the convection chamber and above the combustion chamber, vertical d'owntubes lining the wall of the combustion chamber, means including a motor-driven pump forforcing liquid from the drum into the upper ends of the down-tubes, vertical up-tubes located in the convection chamber and connected between the lower ends of the down-tubes and the` drum, and means including a device responsiveto changes of the condition of the mercury near y the lower ends of the tubes for controlling the operation of the pump-to prevent evaporation of 'mercury liquid in the combustion chamber.

3. A mercury boiler having walls forming a combustion chamber and a convection chamber adjacent the combustion chamber, the convection chamber having a lower end communicating with the combustion chamber-and an upper enlarged portion, a drum located above the combustion chamber and below the enlarged portion of the convection chamber, down-tubes lining the walls of the combustion chamber, 11p-tubes disposed inthe convection chamber and having lower ends connected to the lower ends of the down-tubes. means including a pump for forcing mercury liquid from the drum into the upper ends of the down-tubes, and a bank of inverted convection heating tubes in the enlarged `portion connected in series between the upper ends of the up-tubes and the drum.

v4. A mercury boiler having combustion and convection heating chambers with rows of downincluding a device responsive to changes of the condition of the mercury near the lower ends of the tubes for controlling the evaporation level of the mercury` toprevent evaporation before the mercury liquid has entered the lower ends of the up-tubes. l

ARTHUR R. SM'ITH. 

